When exposed to UV-C light viruses are deactivated by disrupting their DNA / RNA. If sufficient damage is done to the DNA/RNA the cell is then unable to replicate. The most effective wavelength is 254nm, this has the advantage of not producing Ozone so after the cleaning process is complete the area can be entered immediately. UV-C will not only kill viruses on the surfaces it reaches but also any airborne viruses within in its sight.
Each virus/bacteria type requires a different dose of UV-C to ‘kill’ it. Coronavirus (of which COVID-19 is one) requires an average D90 (90% ‘kill’) dose 66J/m2, this extrapolates to 132J/m2 for a 99% ‘kill’ rate. This dose can be delivered by a weak light for a long time or a strong light for a short time. So, the time required to disinfect the virus depends on the power of the light source, distance from the source and type of virus.
The 254-MRD212, mobile UV-C disinfection unit, outputs 24W of irradiated UV-C light at 254nm. At 1.5m this gives a Coronavirus 99% ‘kill’ time of 284s.
UV-C light does not reflect well off all surfaces, therefore areas that are shadowed will not receive the required dosage. The placement of the equipment is important to maximise surfaces in the UV-C line of sight, so that every surfaces receives the required dose in a similar time. The elimination of shadows is achieved in three complimentary ways;
Below are dosages required to kill 99% of various viruses, based on using a 254-MRD212 set-up at a distance of 1.5m.